The invention concerns an optical pick-up for scanning an magneto-optically recorded medium on the three-beam principle, with a diffraction element, whereby the principal beam that has a plane of polarization rotated in one direction is reflected by the magneto-optically recorded medium onto a photodetector and the principal beam that has a plane of polarization rotated in the other direction is reflected by the magneto-optically recorded medium onto another photodetector and whereby the data signal is constructed out of the difference between the photovoltages of the first and the second photodetectors.
The design and function of an optical pick-up for a compact-disk player are described in Electronic Components and Applications 6 (1984), 4, 209-15.
How the Kerr effect is employed to enter information in and read it from an magneto-optic disk is described in "Magnetooptische Versuche dauern an" ["magneto-optic tests continue"], Funkschau 13, 6/20/1986, 37-41.